The US is far from impeaching Donald Trump and removing him from the presidency

The Trump adventure has moved a step closer from being shockingly unconventional to being criminal.

The chairman of a presidential election campaign has been charged with crimes for the first time since the Watergate scandal, the criminal conspiracy that consumed Richard Nixon's presidency in 1974.

For charges including laundering more than $US18 million and conspiracy against the US, Trump campaign chair Paul Manafort is exposed to the risk of some 20 years in jail. His business partner has been charged too. They plead not guilty.

And the third person charged, an adviser to the Trump campaign on foreign policy, has pleaded guilty to lying to FBI agents about his relationships with "certain foreign nationals whom he understood to have close connections with senior Russian government officials", in the words of the charge sheet.

Importantly, this adviser, George Papadopoulos, is co-operating with the continuing investigation by the special counsel, Robert Mueller, according to Mueller's office. This fact is pregnant with risk for the Trump ecosystem.

And all this is just the first set of revelations from the Mueller effort, which is still in an early phase.

Donald Trump's tweeted defence to date is twofold. First: "Sorry, but this is years ago, before Paul Manafort was part of the Trump campaign." This is quite true.

And second: "But why aren't Crooked Hillary & the Dems the focus?" This is irrelevant to the investigation, of course. But it's a signal to his Republican supporters in the US Congress to set up a separate investigation into Clinton to try to create both a diversion, and to establish a political and moral equivalency.

Much excited commentary on this case has raced far ahead of the facts. It's a bid for wish fulfilment - to see Trump impeached and removed from the presidency. The US is far from that point.

First, none of the Mueller material so far goes anywhere near implicating Trump himself in a conspiracy with the Russian government.

Second, even if it did, would the Congress vote to impeach him? Impeachment is not a legal process. It's a political one.

As things stand, it's doubtful that the Congress would impeach him even if there was clear evidence of a finding of collusion against Trump. Why? Because Trump is unpopular with Americans at large, but he's a superstar among Republican voters.

He carries the consistent approval of around 80 per cent of them. That's why the only Republican senators speaking out against him are the ones retiring from politics.

As one of them, Jeff Flake, conceded, the "bottom line" is that "you can't question his behaviour and still be a Republican in good standing". He could not be critical of Trump and still win a primary in his own party. And Republicans have majorities in both chambers of the Congress.

But couldn't prosecutors bring a criminal charge directly against him? The US constitution appears to protect a sitting president from prosecution, although this is keenly contested by constitutional lawyers.

In short, as the political forces are now constituted, there is no clear path to removing Trump even if he is found to have colluded criminally with the Russians.

But the special prosecutor is playing a long game. His first charges are powerful not because they implicate the president - they don't - but because they set up pressures on people who would have information that might, if such information exists.

At least one is already cooperating, and Mueller is plainly hoping that others will, too.

But Trump's enemies need more than evidence. They also need to change the constellation of political power in Washington to give force to that evidence.

To remove a US president, proving criminality isn't enough. He needs to be weakened, too.